mapmerge is package {
  import treemap;
  
  main() do {
    var t := trEmpty;
    for x in iota(1, 10, 1) do {
      t[x] := x;
    }
    
    logMsg(info,"depth of t is $(tree_depth(t))");
    
    var u := trEmpty;
    w is _merge(u, t);
    
    logMsg(info,"depth of w is $(tree_depth(w))");
  }
}